The United States and South Korea are preparing to hold a joint sea exercise, scheduled to begin the day before the expected opening of a rare meeting of North Korea's only political party.

South Korean and U.S. military officials say the five-day exercise is meant to send a strong message of deterrence to North Korea, and also to strengthen the general capacity of joint anti-submarine warfare, says Army Colonel Lee Bung-woo, a spokesman for the South Korean Joint Chiefs of Staff.

The official North Korean newspaper, the Rodong Sinmun, condemned the war games, saying they "may drive the situation to an unpredictable grave phase."

The maneuvers begin the day before North Korea's Workers' Party is scheduled to hold its first meeting since 1966, at which a leadership shuffle is expected. It was originally expected to begin by mid-September, and official North Korean media gave no reason for the delay.

Analysts speculate that at this conference Kim Jong Un, the youngest son of supreme leader Kim Jong Il, will be named to a committee post, the first step for him to eventually succeed his ailing father.

The meeting and the military exercises come as tensions appear to be easing on the Korean peninsula.

The U.S. and South Korea have held a series of training exercises as part of their response to the sinking of a South Korean warship six months ago. An international investigation concluded that a North Korean torpedo destroyed the Cheonan, killing 46 South Korean sailors. Pyongyang denies responsibility. China has joined in North Korea in denouncing the exercises, particularly this one, because it takes place in the Yellow Sea, close to Chinese territory.

In recent weeks, however, rhetoric has cooled. South Korea recently sent aid to help North Korea recover from devastating floods.

North Korea also proposed resuming a program to re-unite long-divided families. On Friday, officials from the Red Cross committees of the two Koreas met at Kaesong, just north of the heavily fortified border for their second round of talks on holding another reunion. The first discussion, a week ago, failed to reach agreement on a venue.

The two Koreas remain at war, technically. Their three-year civil war, which ended with a truce but no treaty in 1953, caused several million civilian and military casualties and separated countless families.